Originally posted 2017-03-22 13:42:37.

COMMON FAULTS IN LATHE MACHINES WITH C.A.D. (micro-computer)

Center lathe popularly called lathe machine is a necessity to every mechanical industry that has works to do with the foundry, metal cutting works, and creation of metallic shapes for engine parts, besides these there are other services this machine can be used. The lathe machines have undergone many modification and improvement in terms of designs and functions.

The type of lathe shown in the diagram above has the design to function with an LCD screen and has keys within the screen location for data input, it makes it easy for dimensions of the desired work to be specified for machining into the processing memory of the late, the computer device which has the screen can be seen attached to the upper left side of the lathe just above the spindle of the lathe it major functions are to specify dimensions for the workpiece the lathe wants to process, store data in the form of written program for a specific machining a particular shape of workpiece, it can also receive data from devices like memory cards, etc. and sends it to the lathe memory which it can interpret for the processing the workpiece. The inclusion of this microcomputer into this modern lathe machine made it be classified as among the machines with COMPUTER AIDED DESIGN (CAD).

The lathe is believed to be among the latest technology in the building of industrial machines and has the ability to operate itself with minimum supervision provided the data inserted through the screen are correct. The machine; according to the manufacturer’s manual is said to have the potential of being in operation for more than six hours without stopping while processing a particular workpiece.

Due to the long length of its sliding bed and its stable alignment with the tailstock, it can be used to process a longer workpiece such as pipes, and beams, without having many problems as compared to the previous types. It has a shield guard for the operator to cover the operating area of the machine and be able to look through the screen in other to see the progress of the machining. It also has an automatic lubricating system to supply lubricants to the parts being machined and assist in the removal of chips produced at the cause of the machining. These and much more are the advantages and features of the lathe machine, but it also has its problems.

According to the discoveries I made, it has the habit of developing some faults which tend to harm its high reputation over a period of time. Some of the problems are listed below:

CRACKS ON THE BED

The lathe has a longer seat bed for the sliding of the tailstock during operation when compare to the previous types, when a critical inspection was done to a certain the type of metal used it making the seat bed or sliding of the lathe machine, it was discovered to be of cast iron probably to be able to withstand the shocks coming from the movement of the workpiece against the cutting tool, as that happens to be the major principle of operation in lathe machines.

The bed enables the machine to process a very long workpiece with the assistant of the tailstock, but on like the previous designs and types of the lathe machine, the bed does brake in pieces when heavy workpiece are machined with the bed constantly. But this hardly happens in previous designs.

According to the machinist, he explained that he enjoy working with the lathe than other types but it little problems which the breaking of bed is among has limited its usage.

He stated that the breaking do not occur instantly, rather it would take a very long process starting with a crack, and as the machine is continuously used the cracks will continue to expand until it establishes link with other cracks to lead to falling off of some parts of the bed and gradually it renders the bed unusable.

He also said the manufacturers did not make any mistake in the material property for the bed rather it could be that the machine was been used above the recommended maximum weight of workpiece since the manual was not handed over to him for study.

Looking at what was obtained in the property of the material which is a cast iron with highly processed surface for smooth movement it could be said that the manufacturers were right in using cast iron or steel due to its well-known ability to resist shocks and impact force coming to it during machining because it would assist it to still maintain its alignment and accuracy on the machining process than when other types of metal are used.

BROKEN GEAR TEETH

Another major problem with the lathe is that over a period of time its gear teeth will start deforming in shape, having some parts chopped off. But this may not be a big problem because the gears can easily be replaced; though it could cost very high in the market but it cannot be compared to the case of a damaged seat bed.

A discovery with some pieces of gears changed previously have indicated a bent in the clockwise direction, which shows that the tendency of the gears to overcome the forces on the cutting tools as the operation is going on makes its teeth to start deforming gradually,  though this may be visible later after about ten years of operation while in most cases it may not be visible rather can be discovered using a precision measuring instrument, in other words, a lathe machine can still be working and performing its operations properly even when the gear teeth have started deforming and breaking off gradually.

The major sign of noticing about this problem in the severe cases is the jerking sound on the workpiece during operation. And little deviations in the accuracy of the machine which I will become a source of error on any finished job by the machine.

The best way to curb this problem is through periodic millwright job on the machine in other obtain the actual deviation from the standard one and to recommend when it is necessary to change the particular gear to new one whose teeth are in the standard dimensions.

LOOSE BELT

The belt linking the machine’s engine made of a very high speed and high torque electric motor with the pulley that carries the spindle in which the workpiece is attached. The belts are in multiple numbers on a single pulley, in other words; the pulley in the electric motor and that on the edge of the spindle is meant to carry four or three belts at once while rotating, the purpose of this design is to ensure that all the forces from the electric motor are well transmitted. But these belts do get loose over a period of time and in the worst situation, one of the belts may cut inside the machine which could pose a serious problem to the remaining belts if the machine is still in operation.  Because of this danger, periodic checks were usually conducted for the belts to ensure anyone that had slacked is removed immediately. meanwhile, some manufacturers recommend changing the four belts at once periodically once anyone of them shows a sign of slack.

DECODING-ERROR

Decoding simply means processing information sent to the system, in this case, the lathe machine being a computer aided design type needs to possess the ability to interpret what the computer has sent into its memory. Though the machine works perfectly in this regard, but report shows that there are times it could not process the information sent properly, either as a result of the error while encoding the data or due to bugs developed within the machine memory, even dirt or water traces in the micro-computer is believed to cause problem in the link that exists between the machine and the micro-computer.

So for a period of time when the machine will not be in use some protective works are usually done to ensure the machine remains in good condition pending till the next use.

VIBRATIONS ON THE FOUNDATION

Another problem that does follow this machine is its creation of vibrations on the foundation. Just like every heavy machine vibration is inevitable but the ability of a machine to minimize its vibration shows a good sign of mechanical balance of the machine both in part setting up and while in function.

The lathe machine can impact great force on the foundation which causes the foundation to crack over a period of time. This could be caused when the machine is used for heavy loads and the foundation was poorly built.

Notwithstanding these problems, the machine still has higher advantages against the smaller types and some bigger types that do not use the micro-computer, but precautions must be put in place while installing and putting it into use; as well as its periodic maintenance schedules and adherence to the manufacturer’s recommendation.

 

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